Aquatic Plant Ecology

Aquatic Plant Ecology
Jennifer Gutscher
M.S. student
South Dakota State University
Nov. 2007

Aquatic Plant Ecology
• Habitat
• Classification
• Major Families
• Life History Strategies
• Seed Ecology
• Abiotic & Biotic Influences
• Competition
• Exotic Species
• Wetland Plant Adaptations
2

What are Aquatic Plants
• “growing in water or on a substrate that is at least periodically deficient in oxygen as a
result of excessive water content” (Cowardin et al. 1979).
• Evolved from terrestrial plants, invading water in 50-100 separate events
• Approximately 60% of aquatic species have ranges on more than one continent
– Due to moderate environmental conditions in water habitats
– Often on certain latitudes N & S of equator, but not between (waterfowl seed dispersal)
• More than ½ of world’s wetlands are in tropical or subtropical areas
• Endemics high in geographically isolated areas
Bacopa monnieri
3

• Roots
– Stabilize sediments
Wetland Plant Benefits
– Can take up metals/pollutants out of sediments
– Roots accumulate nutrients from sediments, release into water column
• Senescence/decomposition & loss of organic compounds from
tissues
• Leaves
– Evapotranspiration returns moisture to atmosphere
– Floating-leaved plants can reduce evaporation off water surface
• Reduce wave erosion on shorelines
• Habitat & forage for invertebrates
• Seed production for waterfowl
• MANY OTHERS!!! Rhynchospora corymbosa
4

• LAKES:
– Lacustrine
– Larger, deeper,
more permanent
– >2 m deep OR...
– >8 ha in size
– Classified by
productivity of water
zone, shape of basin
and # times the
water column mixes
• WETLANDS:
– Palustrine
– Smaller, shallow, dry
out occasionally
– Only moist soil
– Classified by
hydroperiod,
physiognomy (plant
species structure),
sediment types
5

Littoral Habitat
= Edge to limit of rooted aquatic
plants (hydrophytes)
Merritt & Cummins (1996)
– Emergent
• < 2 m deep
• Cyperaceae (sedges), Poaceae (grasses), Juncaceae (rushes), Typhaceae (cattails)
– Floating-leaved attached
• < 4 m deep
• Nymphaeaceae (water lily), Nelumbonaceae (lotus), Potamogetonaceae (pond weed)
– Submerged
• < 10 m deep
• Most rooted, some free float in water column
• Elodea (waterweed), Haloragaceae (water milfoil), Potamogetonaceae (pond weed), 6
Ceratophyllaceae (hornwort), Lentibulariaceae (bladderwort)

Habitat
Merritt & Cummins (1996)
• Sublittoral
– Small zone b/w littoral and profundal zone
– Shade-tolerant plants
• Limnetic
– Open water from surface to where light does not penetrate
– Free-floating
• Lemnaceae (duckweed), Pistia stratoides (water lettuce), Eichhornia crassipes
(water hyacinth)
• Profundal
– Deep water from limit of light penetration to bottom substrate
7

Major Aquatic Plant Families
• CYPERACEAE = Sedges
– Monocot
– Inflorescence = spikelets, usually
surrounded by leaf-like bracts
– Leaves = flat, 3 vertical rows,
alternate, sometimes bladeless
– Stem = trigonous, solid
– Fruit = achene
– Carex (sedge), Cyperus
(flatsedge/nutsedge), Schoenoplectus
(bulrush), Eleocharis (spikerush)
• JUNCACEAE = Rushes
– Monocot
– Inflorescence = terminal
– Leaves = flat to rounded with large vein
divisions, 2 vertical rows, often all basal,
often reduced or sometimes bladeless
– Stem = round, solid
– Fruit = 3-valved capsule, many seeded
– Juncus (rush)
“Rushes are round”
“Sedges have edges”
8
Eleocharis obtusa

Major Aquatic Plant Families
• POACEAE = Grasses
– Monocot
– Inflorescence = terminal, either panicle,
spike, or rame
– Leaves = flat, 2 vertical rows, alternate
– Stem = round, hollow (except at nodes)
– Fruit = grain
– Agrostis (bentgrass), Urochloa mutica
(California grass), Poa (bluegrass)
• ASTERACEAE = Asters/Sunflowers
– Dicot
– Inflorescence = involucrate head
(many little flowers = ray &/or disk
florets), 1+ series of bracts
– Leaves = variable
– Fruit = achene with awns/bristles
– Achillea (yarrow), Solidago
(goldenrod), Erigeron (daisy fleabane)
Ray
Disk
www.wikipedia.com
www.wikipedia.com
9

Major Aquatic Plant Families
• POLYGONACEAE = Smartweeds
– Dicot, annual
– Inflorescence = raceme, terminal panicle,
axillary clusters
– Leaves = simple, alternate
– Stems = swollen nodes with papery
sheath
– Fruit = trigonous or biconvex achene
– Polygonum (smartweed)
• LEMNACEAE = Duckweed
– Inflorescence = rarely seen, tiny
– Leaves = elliptic to oblong
– Roots = hang into water column
– Small to tiny plant
– Free-floating
– Lemna (duckweed), Wolffia
(watermeal)
Polygonum punctatum
Lemna aequinoctialis (large) &
Wolffia globosa (small)
10

Flowering Plants:
Monocot vs. Dicot
11
www.images.encarta.msn

Spikerush
Eleocharis obtusa
MONOCOTS
Nutsedge/Flatsedge
Cyperus polystachos
Climbing dayflower
Commelina diffusa
13

Primrose willow
Ludwigia octovalvis
DICOTS
Valley redstem
Ammania coccinea
Water hyssop
Bacopa monnieri
15

EFFECTS OF MOWING
GROWING POINT
AT BASE
GROWING POINT
AT TIP
MONOCOTS
DICOTS
16

Reproductive Strategies
• Annuals
– Early-successional species
– Colonize disturbed areas devoid of vegetation
– Complete life cycle in one year
– Reproduce entirely by seed – Prolific!
Cyperus difformis
– Seeds remain in seed bank for many years
– Bidens (beggarstick), Echinochloa (barnyard
grass), Cyperus (flatsedge)
17

Reproductive Strategies
• Perennials
– Survive few - many years
– Reproduce by seed, vegetative means, or both
• Shorter-lived species may reproduce entirely by seed
• Most longer-lived species may reproduce by both seed
and vegetative means
– Colonize new areas by seed
– Then, spread extensively by vegetative
reproduction
Sagittaria latifolia
– Many can tolerate extended flooding
• Aerenchyma tissues
• Adventitious roots
– Typha (cattail), Schoenoplectus (bulrush), Boltonia (aster),
Sagittaria (arrowhead), Sparganium (burreed)
19

Seed Bank
• All viable seeds and/or propagules present on or in the soil or
associated litter (Simpson et al. 1989).
• # of spp. in seed bank reflects community diversity better than just what’s growing
– Older wetlands tend to have more total seeds
• BUT!...lots of variation b/w wetlands
– Most seeds are long lived
• Polygonaceae (smartweed), Schoenoplectus (bulrush), Typha (cattail),
Chenopodium (goosefoot)
• Cyclic hydrology (rather than stability) increases seed bank diversity
• Wind, water, birds, fish, etc... disperse seeds
• Sedimentation buries seeds deeper, some decompose
– Seedlings from large seeds can push through soil better than small seeds
21

Seed Bank
• What’s in my seed bank
– Take soil cores, allow germination in diff. abiotic conditions
• Temp., drawdown rate, etc...
– I.D. seeds from samples
– Good to know for restoration projects
• Inaccuracy
– Some quickly predated
– Microorganism attack
• Bacteria
• Fungi
– Dispersal dependants decompose easily
• Phragmites australis (common reed)
– Many plants depend mostly on rhizomes/other asexual reprod. methods
22

Size & Diversity of Wetland Seed Banks
WETLAND
TYPE
DENSITY
(x/m²)
RANGE
(m²)
SPECIES
RICHNESS LOCATION REFERENCE
FRESH 29,753 10,875 - 36,230 45 IOWA VAN DER VALK
AND DAVIS (1978)
FRESH 110,000 42,000 - 255,000 50 IOWA VAN DER VALK
AND DAVIS (1979)
TEMPORARY 17,943 11,455 - 24,430 21 NEW JERSEY MCCARTHY (1987)
BRACKISH 3,577 93 - 8,253 34 MANITOBA PEDERSON (1981)
LAKESHORE 10,089 1,862 - 19,798 41 ONTARIO KEDDY AND
REZNICEK (1982)
RIVERINE
SWAMP
2,576 759 - 4,392 59 SOUTH
CAROLINA
SCHNEIDER AND
SHARITZ (1986)
SALT 191 50 - 430 3 UTAH KADLEC AND
SMITH (1984)
ADAPTED FROM LECK (1989)
23

Dispersal Mechanisms of Seeds
Animal
Dispersal Agent &
Adaptations
Chemical attractant
Clinging Structures
Modification
Hooks, Viscous material
colored seed coat
Comments
Sticks to fur/feathers
Eaten by birds
Wind
Size reduction
High Surface/Volume
Ratio
Dustlike seeds
Wings, plumes,
Balloons
Up to Millions/plant
Balloons uncommon
Water
Resistance to sinking
Uses surface tension
Low specific gravity
Hairs or slime
Small Size, Unwettable
Air spaces, Cork, Oil
Submerged transport
Float until wetted
Float long distances
25

Seed Longevity
Species
Age
(years)
Naturally
Preserved
Natural Field
Conditions
Location
Lupinus arcticus
(Arctic Lupin) 10,000 +
Yukon Territory
Chenopodium album 1,700 + Scandinavia
Spergula arvensis 1,700 + Manchuria, Tokyo,
Great Britain
Nelumbium nucifera
(Indian lotus)
100 – 3,000 + Argentina
Canna compacta 550 + Michigan
Rumex crispus
(Curled dock)
Oenothera biennis
(Evening primrose)
80 + Michigan
80 + Michigan
Amaranthus retroflexus
>30
+
Michigan
Setaria media
>30
+
Michigan
Agrostis vulgaris

Depth of burial
• 3 cm deep
• Can bring up seeds from
inactive depths through
tilling/discing/scraping
28

What you see is not always
what you have!

Seed Bank & Standing Veg. Species
Diversity
Wetland
type
Seed
Bank
Veg Total Location Reference
Fresh 45+ 34 48 Iowa
Van Der Valk &
Davis (1978)
Temporary 21 29 31 New Jersey
McCarthy (1987)
Brackish 29+ 18 35 Manitoba
Pederson (1981)
Lakeshore 41 45 50 Ontario
Keddy &
Reznicek (1982)
Riverine
Swamp
59 49 73 S Carolina
Schneider &
Sharitz (1986)
Salt 9 14 15 Utah
Kadlec & Smith
(1984)
30

Using Seed Banks to Your Benefit
Seed banks can be exploited to promote desirable vegetation communities
Success depends on:
1. Presence of seeds of preferred species
2. Suitable conditions for germination and establishment of preferred species are
met
3. Absence of seeds of unwanted species, or these seeds are uncommon
4. Conditions for germination and establishment of unwanted species are not met
31

Hydrologic Germination Requirements
• Each species responds to a unique combination of abiotic and biotic factors to break
dormancy and/or germinate
– Requirements can be very different from what mature plants can handle
• Drawdown
– Most all emergents
– Potamogeton (smartweed), Fimbristylus littoralis (fimbry)
• Flooding
– A few emergents, i.e. Sparganium (burreed)
– Most all submergents
– Najas guadalupensis (Southern naiad)
Fimbristylus littoralis
• Wet meadow hardest to reestablish
– Generally poor dispersers
– PLUS, can’t persist in seed bank
– Carex (sedge)
32

Rock
Lichen & Moss
Weathering &
Erosion
Ferns
Grasses
Forbs
Succession
• Germination sets in motion a
pathway of succession
Annuals
Perennials
• IF NO DISTURBANCE:
– Lower Seed Production
– More Perennials
– More Woody Vegetation
Shrubs
Seedlings
Trees
33

Influences on Aquatic Plant
Communities
• Position in Landscape
• Hydrology
• Soils
• Light
• Temperature
• Water chemistry
• Seed bank
• Competition
• Other Biota
34

Wetlands in the Landscape...
Relationship with Hydrology
Discharge
Flow Through
Recharge
35

Recharge
Wetland Types
Discharge
Flow-through
36

Hydrologic Disturbances
• Wet conditions
– Submerged, floating-leaved, emergent plants, and algae
• Dry conditions
– Emergents, mud-flat annuals
• What makes conditions change
– Yearly/cyclical fluctuations in water quantity
– Hydrologic disturbance of nearby river, lake, etc...
– Floods
• Can bring in new sediment, remove the old change vegetation community
– Hurricanes/Tornados
• Can create patchy network of vegetation
– Water quality
• Like pushing “reset” button on succession
37

Typical Zone Vegetation
• Aquatic
– Nearly continuous flooding at low elevations
– Potamogeton (pondweed)
• Marsh
– Most flooded for majority of growing season
– Fimbristylus (fimbry)
Fimbristylus littoralis
• Wet Meadows
– Occasional flooding kills woody plants
– Cyperus (nutsedges/flatsedges)
Shrubs
• Shrubs/Forested Wetlands
– Periodic flooding (part of year – multiple years)
– Not enough flooding to kill woody vegetation
– Salix (willows)
Marsh
Wet
Meadow
Amplitude of
long-term
water
fluctuations
Aquatic
38
Adapted from Cronk & Fennessy 2001

Wetland Hydrologic Controls
• Stabilizing water levels (2 - 3+ yrs) can reduce plant species and community diversity
– Significantly reduce emergent vegetation cover
– Increase open water
– Increase # & dominance of exotics/aggressive perennials
• Typha (cattail) and Urochloa mutica (California grass)
– Allow monospecific vegetation stands &/or one structural type
– Decrease species richness
– Decrease fungal or pollinator mutualistic relationships
– Reduce or eliminate wet meadow and/or marsh zone
Shrubs
Marsh
Wet
Meadow
Amplitude of
long-term
water
fluctuations
Shrubs
Aquatic
Aquatic
39
Adapted from Cronk & Fennessy 2001

Riverine Hydrologic Controls
• Tropical rivers flood during “rainy season”
– Riparian plant community composition dependant on physical disturbance
• Intermediate disturbance hypothesis (Cronk & Fennessy 2001)
– Too little disturbance “competitive exclusion tends to reduce diversity”
– Too much disturbance “only highly tolerant species are able to persist”
• Plant diversity also dependant on:
– River discharge velocity
– Stream order
– Soils
– Microtopographic relief
– Upstream plant diversity
40

Soils
• Soil temperature
– Affects germination
• Soil Color
– Can change with redox reactions
• Microbes obtain O2 from mineral oxides = reduction
– Indicates hydric soils
• Soil Texture
– Ribbon test
– Gritty sand loamy silt soft, tight clay
• Soil moisture
– Capillary fringe
• Rises higher with tighter pores
• Found w/in 12” of soil surface = wetland
– High organic content slippery feel, easily deformed
41

Soils
• Organic Content
– Black, porous, light weight, smelly hydric
• Methane & sulfide are smelly!!! redox rxn hydric soil
• Residual Plant Material
– Anoxic conditions slow plant decomposition
• Soil Stratigraphy
– Cognizant of horizons
• Mineral composition helps control hydrology & water chemistry
– Clay soils hold water
– Sand lenses transmit water laterally
– Hard Fe (iron) precipitate in HI bogs can cause ponding
• Hydric soils – get down 45 cm (18”) to test
• Soils become hypoxic within a few days of flooding anoxic
42

Light
• Most important factor for submerged plant distribution
•

Light
• Suspended solids, dissolved organic and inorganic compounds
– Scatter light & absorb heat
– Boat traffic, shoreline erosion, bottom feeding fauna, high wind action
• Heavy periphyton coating can reduce productivity
• Shading by other vegetation
• Residual plant material
• Time of Year
– Day length
– Intensity of light
45

Temperature
• Water
– Fluctuations much less rapid and extreme
• Increases “cosmopolitan species”
– Phragmites australis (common reed), Lemna spp.
(duckweed), Ceratophyllum demersum (hornwort/coontail)
– High specific heat of water thermal stability
– Solar radiation only reaches the uppermost few meters & affects...
• Aquatic plants, O2, chemicals, aquatic insects, etc...
• Plants
– Increase ET
• Lose more H2O when open pores to intake CO2, exhale O2
• Soil
– Increase in temp. fluctuations can incite germination
47

Water Chemistry
• Soil & bedrock composition is huge influence
• Higher pH, conductivity higher site fertility more spp. richness
– pH
• Increases during day use CO2 less carbonic acid (H2CO3)
• Decreases at night opposite rxn.
• Higher in urbanizing areas
– Conductivity (μS/cm)
• Total dissolved salts (TDS) or total dissolved ions
• Increases with more evaporation (concentrates salts)
• Bigger watershed more contact with soil before entering water
more ions
• Too many accumulated ions can be toxic
–Ca 2+ , Mg 2+ , SO 4-
, CO 3
2-
, HCO 3-
, Cl - , Na +
49

Water Chemistry
• Dissolved gases
– O2
• Oxidated, hypoxic, or anoxic soils
– Most plants require soil O2 levels high enough for respiration in
order to germinate
– Echinochloa crus-galli (barnyard grass) can germinate in anoxic
conditions
• Floating vegetation mats heavy shading reduces submerged
vegetation/phytoplankton reduces O2
• Decomposition increased O2 demand by bacteria reduced O2
– CO2 sometimes limiting factor in submerged communities
50

Water Chemistry
Leptochloa fusca
• Salinity
– Brackish = 0.5 ppt (1.4% seawater)
– Fresh water hard to obtain
– Necessary ion uptake more difficult
– CO 2 uptake difficult (opening stomata incurs water loss)
– Reduces plant productivity
– Toxic to freshwater plants
• Can be used to your advantage!
• Nutrients
– Phosphorus tends to be limiting nutrient in oligotrophic systems
• [N] = 1.5% (Cronk & Fennessy 2001)
• [P] = 0.13%
– Nitrates common in fertilizers/runoff
• Pollutants
– More in human land use areas
– Ammonia, orthophosphate, chloride
– Can change vegetation community
51
Batis maritima

• Trails form open water pathways
Biotic Influence
• Forage
– Plant often dies b/c oxygen supply is cut off
– Can change plant community
• Decreases amount of certain species, allowing others to outcompete
• Nesting materials
– Wider less strands needed
– Tougher less likely to break down
– More aerenchyma floatation
• Droppings increase plant productivity
USFWS
• Can increase open water habitat
52

Plants Compete Too!
• The better competitors:
– Make more biomass
– Can gather nutrients when they’re at low levels (& still survive!)
• However, high nutrient enrichment (eutrophication) decreases spp. richness
– Exotics often win this competition
• Increasing MICROtopography...
– Increases heterogeneity
– Increases # individual plants
– Increases biomass
– Reduces competition
53

Plants Compete Too!
• Light
– Floating-leaved plants can shade out submerged spp., esp. if high turbidity
• Nymphaea (water lily)
– Submerged spp. can form mats to shade out new growth from bottom
• Ceratophyllum (hornwort)
– Some emergent monocots reproduce vegetatively, shade out
submerged/floating
• Carex (sedge), Cyperus (flatsedge/nutsedge), Typha (cattail)
• Nutrients
– Ability to assimilate nutrients faster is advantage
Nymphaea capensis
54

Schoenoplectus juncoides
Plants Compete Too!
• Space
– Dense, monospecific stands produced by vegetative growth
– Fire
• Myriophyllum (water milfoil)
• Increases space less aboveground standing stock reduces
competition
• Increases nutrient availability through oxidation (from plants to free in soil)
• Maintains current stage or resets succession
• Was it a part of natural regime
• Deep water
– Diffusive O2 flow to roots outcompeted by pressurized O2 ventilation
• Pressurized in some spp. of Nymphaea (water lily), Eleocharis
(spikesedge), Schoenoplectus (bulrush), Typha (cattail)
– Skinny, tall leaves can be better in deep water than short, wide leaves
55

• Competitors
– Low disturbance
– High productivity habitat
– Low reprod. ability, high growth rate
– Capture available resources well
• Biomass storers
– Low disturbance
– Low productivity/low light/high
salinity
– High vegetative reproduction
– Rhizomes/tubers store biomass
and nutrients
Elodea (waterweed)
Typha (cattail)
Carex echinata
(star sedge)
Polygonum punctatum
(dotted smartweed)
• Ruderals
– High disturbance (not competitive)
– High productivity habitat
– High reprod. ability, fast growth, short life
– Annuals - disperse!
• Stress-tolerators
– High disturbance
– Low productivity habitat
56
– Low reprod. ability, low growth rate

• Secondary metabolic compounds
– Root exudates
– Leached from leaves or litter
Allelopathy
• Thought that chemicals are “expensive” to make, so usually “compete using
only its physiological adaptations” (Cronk & Fennessy 2001)
– Therefore, chemicals only produced under crowding stress
• Cyperus (flatsedge), Eleocharis (spikesedge), Polygonum (smartweed),
Nuphar (water lotus)
57
Nuphar (water lotus)

Why are Exotic Species so Competitive
• Rapid regeneration through prolific seeds & vegetative reproduction
– “The vegetative spread of submerged or floating species is most rapid in the
tropics and where water levels remain constant” (Cronk and Fennessy
2001).
– Eichhornia crassipes (water hyacinth) can double areal extent in 3.5 days
• Pests/herbivores not evolved to attack/consume exotic plant
• Little competition from other plants
– Native plants evolved to exploit separate niches
– Exotics’ competitors rarely present in new range
– Can grow quickly by capturing resources & light
58

Why are Exotic Species so Competitive
• Aquatic environment is relatively uniform
• Wide ecological tolerances (generalists)
– Can become dominant most anywhere if given the chance
• Many are cosmopolitan (occur across the world)
– Pistia stratoides (water lettuce)
• Some resistant to fire, flood, drought
Pistia stratoides (water lettuce)
59

Exotic Species...
• ...on Islands
– Proportion of exotics on islands...up to 50%
• Proportion of exotics on continents...up to 20%
– Hawaii
• Few plants colonized mostly evolved once they got here
• Generally no frost would eliminate many exotics
• Transportation stop b/w Asia & N.A.
• ...on Disturbed areas
– Very susceptible to invasion
– Natural Fire, flood, drought, biota
– Human
• Damming/impoundment
• Fragmentation
• Urbanization
• Pipes/irrigation/drains that change salinity
• Climate change
– Coastal areas
– Weather pattern changes
– Veg. movement towards poles
60

Invasive Infestation
• Change community structure
– Rhizophora mangle (red mangrove) planted on Oahu
• Shade out natives
• Dense root system altered animal movements & community
• Altered soil O2
• Hybridize with natives
– Can be more adapted, but just as invasive
• Reduce seed bank diversity
• Draw water level down with high evapotranspiration rates
– Surface & ground water
61

Invasive Infestation
• Thick submergents
– Provide refuge for fish fry, allowing high survival overpopulation,
stunting
– Hard for predator fish to hunt
• Dense floating mats
– Eichhornia crassipes (water hyacinth)
• Inhibit O2 diffusion into water kill fish, invertebrates, plants
• Accumulate heavy metals & toxic compounds ingestion can kill
animal
– Hard for chicks to maneuver
• Alters fire regimes
– Dry leaves of Arundo donax (Spanish reed) catch fire easily
• BUT...plant is fire-tolerant
62

Invasive Plant Growth Requirements
Species
American
Lotus
Common
Reed
Reed
Canarygrass
Broadleaf
Cattail
Narrowleaf
Cattail
Salinity pH range Propagated
Tolerance
None 4.59 – 7.40 Seed
Low 4.50 – 8.0 Sprig
Low 5.50 – 8.0 Seed and Sprig
Low 5.50 – 7.50 Sprig
Medium 3.70 – 8.50 Seed and Sprig
63

Nuphar rhizome
Biomass of Vegetatively
Reproducing Perennials
• Need to consider below ground biomass more!
Mowing to cut off meristematic tissue is often not enough
Must grub/scrape/dig to disrupt rhizomes/tubers
Production (lb/acre)
Species Common name Above Below
Phragmites Common reed 9,580 64,060
Typha Cattail 7,580 16,060
Nuphar Water lotus 5,400 10,225
65

Adaptations
• Roots
– Adventitious = laterally from main stem base into soil surface
• In positions they normally don’t occur
• Replace deep roots that die b/c anoxia
• Stabilize & increase O2 to roots
• Salix (willow), Rumex (dock)
– Shallow rooting
• Allows access to NO3- (nitrate), and O2
– Prop & drop roots on red mangrove plants
• Covered with lenticels for O2/CO2 exchange
• Stability
– Buttressed trunks
• Jurassic Park
Sagittaria latifolia
• Stems
– Elongation to access light, O2, CO2
• Sagittaria latifolia (arrowhead)
66

Adaptations
• Rhizomes
– Larger carbohydrate storage allows more ATP production for cell metabolism
• More ATP needed in anoxia
– Phragmites australis (common reed), Schoenoplectus (bulrush), Typha (cattail)
• Aerenchyma = tissue with large intercellular spaces (lacunae)
– O2 to roots, brings CO2 from roots & out stomata
– May be 50-60% of root area in flood-tolerant plants
– Stem floating to access light, O2, CO2
– Swelling at stem base to enhance aeration
– Some invertebrates tap into this to respire
• Coleoptera larvae (Donacia sp. - Chrysomelidae)
• Diptera larvae (Mansonia sp. – Culicidae
& Chrysogaster sp. – Syrphidae)
Schoenoplectus
juncoides
67

Adaptations
Ludwigia palustris
• Leaves
– Some float off long stems, spread out to access light, O2, CO2
– Heterophylly
• Emergent leaves ovate/elliptic/rounded
• Submerged leaves ribbon-like/dissected
• Ludwigia palustris (marsh seedbox), Sagittaria (arrowhead)
• Chemical defenses
– Herbivory
• Nymphaeaceae (water lily), Arundo donax (giant reed), Colocasia
esculenta (taro)
• Against invertebrates: Ceratophyllum (hornwort), many submergents
68

Adaptations
• Salinity
– Increase internal solutes freshwater comes in
Batis maritima
– Exclude or secrete salts, leaf shedding, leaf/shoot succulence
• Nutrients
– Mycorrhizae = symbiotic fungi
• Approx. 85% of all aquatic plants
• Increases water, P, N, K + available for plant, takes carbohydrates from
roots
– N-fixing bacteria in root nodules
• Sesbania (legumes), Alnus (alder), grey, white, and red mangrove plants
– Move nutrients from aboveground tissues to roots, rhizomes, tubers, bulbs
• Energy for start up next growing season
69

Submergence Adaptations
• Leaves
– Chloroplasts in epidermis
– Ribbon-like or highly dissected
• More light to chloroplasts
• More surface area for gas &
nutrient exchange
• Shoots can absorb water & nutrients
• Less xylem & lignification
• More aerenchyma
– Buoyancy for proximity to light, O2, CO2
– More gas transport
• Dissolved bicarbonate (HCO 3- ) in photosyn.
– Myriophyllum spicatum (Eurasian water
milfoil)
• Recycle CO2 from respiration into photosyn.
– Elodea nuttallii (western waterweed)
• Thin cuticle
• No stomata
– Gas exchange through diffusion
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Threats
• Wetland loss
– 50% loss on U.S. mainland
– 1/3 T&E plant spp. in U.S. depend on wetlands
• 30 T&E wetland plants in Hawaii alone
• Hydrologic alterations
– Agriculture
– Groundwater drawdown
– Flood control
– Stabilized water levels
• Altered topography
• Pollution
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Threats
Urochloa mutica
• Exotic species
– 20 spp. exotic biota introduced to HI/year
– Monocultures less biodiversity
– Extirpation of native species
– Alter nutrient cycles
– More invasives with more ecosystem degradation
• Global climate change
– Some wetlands will dry up (i.e. seasonal), others will expand
– E.P.A. estimates 15-34 cm sea rise in next century (65 cm
possible)
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Strategy
• Monitoring
• Limit Exotics & Perennials
• Multiple Treatments
• PATIENCE
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H.Gee

HOW
• Set Back Succession
– Flooding/Drawdowns
• Gradual basin slope ideal
– Small drops in water level can expose large areas
• Must understand water budget before flood/drawdown
• Impact on invertebrates, waterfowl, other fauna
– Tilling/Discing
• Consider high degree of substrate disturbance
– Mowing
• Consider meristematic tissue (monocots vs. dicots)
– Herbicides
• Consider impacts on desired species
• Get down to mineral soil
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THANK YOU!!!
jennifer.gutscher@sdstate.edu
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Literature Cited
• Cronk, J. K., and M. S. Fennessy. 2001. Wetland Plants: Biology and Ecology. Lewis
Publishers. Boca Raton, FL.
• Erickson, T. A., and C. F. Puttock. 2006. Hawaii Wetland Field Guide. Bess Press
Books. Honolulu, HI.
• Larson, Gary. 2005. Aquatic Plants. South Dakota State University. Brookings, SD.
• Merritt, R. W., & K. W. Cummins. 1996. An Introduction to the Aquatic Insects of
North America, 3 rd ed. Kendall/Hunt Publishing Company. Dubuque, IA.
• Ward, J. V. 1992. Aquatic insect ecology, Vol. 1. John Wiley & Sons, Inc. New York,
NY.
***Thanks to Hugo Gee for many of the vegetation pictures
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